Diethyl Oxalate → 2,4-Dioxo-4-phenylbutanoic acid

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To a stirred solution of diethyl oxalate (21.9 g, 150 mmol) and sodium ethoxide (168 mL, 21% wt. solution, 450 mmol) was added dropwise a solution of acetophenone (18 g, 150 mmol) in ethanol (120 mL). The reaction mixture was allowed to stir at ambient temperature for 15 h. The reaction mixture was concentrated to ca. 70 mL and partitioned between diethyl ether (50 mL) and water (200 mL). The phases were separated, and the aqueous layer adjusted to pH=1 with conc. HCl before being extracted with diethyl ether (3×100 mL). The combined ether extracts were dried over MgSO4 and evaporated to yield 2,4-dioxo-4-phenylbutanoic acid. 1H NMR (DMSO-d6, 300 MHz) δ 8.05 (d, J=7.2 Hz, 1.8H enol form), 7.96 (d, J=6.9 Hz, 0.2H keto form), 7.69 (t, J=7.5 Hz, 1H), 7.56 (t, J=8.1 Hz, 2H), 7.08 (s, 0.9H enol form), 4.56 (s, 0.1H keto form). 13C NMR (DMSO-d6, 75 MHz) δ 190.7, 170.7, 163.6, 135.1, 134.6, 129.7, 128.4, 98.5.

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